#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main()
{
	char s1[80]="0",s2[80]="0";
	int a,count;
	gets(s1);
	gets(s2);
	for(count=0,a=0;a<80;a++)
	{
		count=count+s1[a]-s2[a];
    }
	
	printf("%d",count);
	return 0;
}
